R205 Sample ID R205 • Cabinet B obsidian 95cm W x 66.4cm H x 66.7cm D • 400g Sample TypeRockRock QualityIgneousRock TypeExtrusive CompositionFelsicTextureGlassyColor Index Clast SizeAcid ReactionMohs Hardness 6 thick wedge shaped chunk with a very sharp edge. top is very smooth and has concentric rings from being chipped off. Description of Mohs scale here